1. Field of the Invention
The present invention relates to casting cores and methods for forming a cored water jacket chamber within a cast cylinder block.
2. Description of the Prior Art
Most automobiles today are equipped with water-cooled engines having cast iron cylinder blocks. The cylinder block is formed with a number of piston cylinders in which pistons of the engine reciprocate. The reciprocating action of the pistons generates a tremendous amount of frictional heat which must be removed for the engine to continue working. Thus, it is common to provide a water jacket chamber within the cylinder block that completely surrounds each cylinder and in which coolant water is circulated for cooling the cylinder walls of the block during operation.
In order to make the engine more compact, the cylinders are spaced as closely together as practical. In practice, this means that the web of casting material separating adjacent cylinders is just wide enough to allow a conventional sand core to be used to form a water passage bypass through the webs cylinder block material to provide cooling between the cylinders. Any closer spacing would prohibit the use of such sand cores as they would be to fragile.
In an effort to reduce the weight and increase the efficiency and performance of these types of engines, automobile manufactures are turning toward lighter weight aluminum cylinder blocks as replacements for their heavier cast iron counter parts.
These aluminum cylinder blocks are typically provided with cylinder liners made of high wear resistant materials. These liners are secured within the cylinder block during casting or in a subsequent operation.
A problem arises, however, when one attempts to cast a water jacket into such a cylinder block having lined cylinders. Since the spacing of the cylinders has already been determined and fixed according to cast iron block standards, the web of aluminum cylinder block material is substantially diminished in size due to the addition of the cylinder liners. In fact, each web is reduced by an amount equal to twice the wall thickness of the cylinder liners. As mentioned previously, conventional sand coring techniques cannot be used to form the water bypass passages between adjacent cylinders having such a small web. As a result, it is common to employ a conventional sand core and simply eliminate the water bypassages in the block.
The U.S. Pat. No. 4,917,169, granted Apr. 17, 1990 to Melde-Tuczai et al. discloses a composite core for forming a water jacket chamber within a cylinder block having closely spaced cylinders. This patent teaches using a costly sintered ceramic material to form the water passage bypass which must be sand blasted out of the cylinder block following casting.
The U.S. Pat. No. 2,991,520 discloses a core in which a sleeve of refractory material is disposed about a support element for forming cored passages in metal castings. There is no teaching, however, of using such a core in combination of other core types such as conventional bonded sand cores to form a water jacket chamber within a cylinder block.